Problem: $2np + 5nq + 10n - 1 = 3p - 7$ Solve for $n$.
Solution: Combine constant terms on the right. $2np + 5nq + 10n - {1} = 3p - {7}$ $2np + 5nq + 10n = 3p - {6}$ Notice that all the terms on the left-hand side of the equation have $n$ in them. $2{n}p + 5{n}q + 10{n} = 3p - 6$ Factor out the $n$ ${n} \cdot \left( 2p + 5q + 10 \right) = 3p - 6$ Isolate the $n$ $n \cdot \left( {2p + 5q + 10} \right) = 3p - 6$ $n = \dfrac{ 3p - 6 }{ {2p + 5q + 10} }$